Phthalate esters are plasticizers incorporated into nearly all plastic materials. The biochemical and ultrastructural effects of di(2-ethylhexyl)phthalate (DEHP) and related chemicals are being studied in order to assess potential mechanisms of phthalate ester toxicity. Since DEHP and other phthalates are also male chemosterilants and teratogenic in mice, studies are being conducted to determine the role of zinc in the pathophysiology of these reproductive effects and to discern no-observed toxic effect levels.